1. Field of the Invention
The present invention relates to a cable structure in an electronic endoscope, particularly to a cable structure in an electronic endoscope in which a video signal is outputted from a solid-state imaging device provided in a distal end assembly of the electronic endoscope.
2. Description of the Related Art
An electronic endoscope has a solid-state imaging device such as a charge-coupled device (CCD), which is arranged behind an imaging optical system provided within a distal end assembly of an insertion part. The CCD is mounted on a CCD board made of ceramics and the like, and a number of leads are connected to terminals provided on the CCD board.
A set of the leads composes a multi-core cable, which comprises the leads (now referred to as core leads), a conductive meshed shield and an outside insulator or a sheathing. The multi-core cable is connected with a processor, which processes a video signal outputted from the CCD and transmitted through the core leads, and the subject image is displayed on a monitor device.
As seen from FIG. 8, the conventional multi-core cable is constructed in which an insulator tape 9 is wound around the core leads 1, and further the core leads 1 are covered with the conductive meshed shield 2 and an outside insulator or a sheathing 3. The meshed shield 2 is connected with a ground lead 4 within the insertion part of the endoscope, and the sheathing 3 is connected with an outside insulator or a sheathing 5 that covers the ground lead 4 and the core leads 1.
Japanese Patent Application Publication No. 6-285020 discloses a connecting structure between the meshed shield 2 and the ground lead 4. FIG. 8 shows an applied example where the sheathing 5 is provided at the board side of the connecting part. In the applied example, the meshed shield 2 is extended from the sheathing 3 and twined, and the ground lead 4 is soldered with the twined part. Inside the connecting part of the meshed shield 2 and the ground lead 4, the core leads 1 is covered with a protection tube 6, so that the meshed shield 2 and the ground lead 4 are prevented from damaging the core leads 1 and from causing a short-circuit, due to their contact with the core leads 1 in a case where ends of the meshed shield 2 and the ground lead 4 are untwined. Moreover, two attachment tubes 7 and 8 are arranged over the connecting part between the meshed shield 2 and the ground lead 4. The protection tube 6 and the attachment tube 7 hold near the connecting part of the meshed shield 2 and the ground lead 4, and the attachment tubes 7 and 8 pinch the sheathing 5. The sheathing 3 and the sheathing 5, which have different diameters, are connected with each other by the protection tube 6 and attachment tubes 7 and 8.
Consequently, the multi-core cable is thick since the conventional cable structure requires the protection tube 6 and the attachment tubes 7 and 8.
The multi-core cable has been desired to be as thin as possible because the insertion part of the electronic endoscope already has a forceps channel, a wire guide for adjusting focus, an angle control wire, air and water supply channels, and so forth arranged therein before the multi-core cable. Spaces used for arranging the forceps channels are limited if the multi-core cable is considerably thick.
The present invention has been developed in view of the above-described circumstances, and has as its object the provision of a cable structure of an electronic endoscope with which the multi-core cable can be thinner.
In order to achieve the above-described object, the present invention is directed to a cable structure arranged in an insertion part of an electronic endoscope, the cable structure comprising: a first lead; a conductive shield member which covers the first lead; a first non-conductive covering member which covers the first lead and the shield member; a second lead which is connected to the shield member at a connecting part; and a second non-conductive covering member which covers the first lead and the second lead, an end of the second covering member being connected over an end of the first covering member, wherein: the first covering member has an opening at the connecting part so that the shield member is exposed and connected to the second lead through the opening; and the second covering member covers the end of the first covering member including the opening so as to cover the connecting part.
According to the present invention, the second lead is connected with the shield member through the opening formed on the first covering member, so that the connecting part between the second lead and the shield member can be contained in the opening. Therefore, the connecting part cannot be bulky and the cable structure can be thinner.
Moreover, since the connecting part between the second lead and the shield member is arranged in the opening formed on the first covering member, the second covering member can be directly connected over the first covering member, and further the end of the shield member and the end of the second lead can be prevented from directly contacting with the first lead. Hence, the conventional protection tube and attaching tubes are not required, and the cable structure can thus be thinner.
Preferably, the cable structure further comprises a heat-contractive tube which covers the first and second leads and the other end of the second covering member, the other end of the second covering member having a notch, wherein when the heat-contractive tube is contracted with heat, the other end of the second covering member is fastened with the heat-contractive tube with respect to the first and second leads.
According to the present invention, the notch is formed at the other end of the second covering member that is covered and fastened with the heat-contractive tube, and the notch is closed when the heat-contractive tube is contracted with heat. Hence, the fastened end portion of the second covering member has no wrinkles and does not warp, so that the heat-contractive tube can be thinner after the contraction.